As catalysts for the production of urethane foam, there have been used tin catalysts and amine catalysts. In view of the restriction on chlorofluorocarbon (CFC) gases, there has been a demand for an amine catalyst which could strongly accelerate the reaction between water and the isocyanate group (foaming catalysts).
Amine catalysts have a strong foaming property in comparison with tin catalysts. Above all, as especially strong foaming catalysts, there are N,N,N',N',N"- pentamethyl diethylenetriamine and bis(2-dimethylaminoethyl) ether.
However, the above two catalysts have high vapor pressure and objectionable odor so that they deteriorate the working environment in the urethane production process. Further, the former has a large temperature dependency, and at the initial stage of foaming, i.e., when the reaction temperature is low, it remarkably accelerates the foaming reaction, but when the reaction temperature rises, it also accelerates the resin-forming reaction so that t becomes difficult to keep the balance between the two reactions. Further, for both catalysts, when either one is solely used in a urethane foaming recipe, the time from the start of stirring of the raw materials to the start of foaming (cream time) becomes extremely short. Therefore, when sufficient amount of catalyst is added to ensure a time for completion of curing (demold time) which is preferred for the urethane foam production process, it becomes impossible to secure the stirring time necessary for the even mixture of the urethane foam materials.